It seems that a number of US scientists spent a number of years with an alien race on their planet before returning to earth.

The information began to be released on 2 November 2005 by a retired senior official within the US Defense Intelligence Agency (DIA) who calls himself "Anonymous". Until he chooses to make his name known, this is the way he will be represented here. Anonymous reports that he is not acting individually and is part of a group of six DIA personnel working together as an alliance: three current and three former employees. He is their chief spokesman.

"We already have the means to travel among the stars, but these technologies are locked up in black projects and it would take an act of God to ever get them out to benefit humanity.... Anything you can imagine, we already know how to do."

Ben Rich, former Head of the Lockheed Skunk Works, in a lecture shortly before he died